/Engine/Source/Developer/CollectionManager/Public/ICollectionManager.h
Event for when collections are re-parented (params: Collection, OldParent, NewParent)
class FCollectionReparentedEvent : public TBaseMulticastDelegate_ThreeParams< void, const FCollectionNameType &, const TOptional< FCollectionNameType > &, const TOptional< FCollectionNameType > & >